The mother of two men kidnapped at the higher education ministry in Baghdad pleads for information about her sons. Photograph: Mahmoud Raouf Mahmoud/Reuters

Dozens of people were killed and scores kidnapped today as insurgents in Iraq unleashed new levels of violence.

Up to 150 academics, staff and visitors were abducted when around 80 gunmen stormed a Baghdad research institute in the largest mass kidnap since the overthrow of Saddam Hussein more than three years ago.

In other attacks, at least 82 people were killed or found dead around the country. The worst violence occurred when a car bomb exploded in the Shia suburb of Sadr City, killing at least 21 people and wounding 25. There were also reports that up to 31 people had died in the Sunni stronghold of Ramadi in what local people said was a US military raid.

Today' s events unfurled as Tony Blair addressed a Washington panel that is considering George Bush's strategy on Iraq.

The armed kidnappers - wearing interior ministry commando uniforms - arrived at the research institute, at the ministry of higher education in the religiously-mixed Karrada area, in a fleet of 20 vehicles at around 9.30am local time (0630 GMT), authorities said.

Alaa Makki, the head of the Iraqi parliament's education committee, interrupted a parliamentary session to say that between 100 and 150 people, a group comprising both Shias and Sunnis, had been abducted. Three were later found unharmed in an eastern suburb. The fate of the others is unknown.

Mr Makki urged the prime minister, Nuri al-Maliki, and the ministers of the interior and defence to respond rapidly to what he described as a "national catastrophe".

He said the gunmen had a list of names of those to be abducted, and claimed to be on a mission from the government's anti-corruption body. The kidnapped included the institute's deputy general directors, employees and visitors.

Iraq's higher education minister, Abed Theyab, instantly ordered all universities to be closed until security was improved, saying he was "not ready to see more professors get killed".

"I have only one choice, which is to suspend classes at universities," he told the Iraqi parliament.

He said the mass kidnapping had been "a quick operation", taking between 10 and 15 minutes, with the gunmen moving throughout the four-storey institute building.

Police and eyewitnesses said around 80 gunmen closed off streets surrounding the ministry of higher education and the research institute, which is responsible for granting scholarships to Iraqi professors and students wishing to study abroad.

A female professor, who was visiting the institute as the kidnappings happened, said the gunmen forced men and women into separate rooms. The men were then handcuffed and herded on to around six pickup trucks.

The gunmen - some of them masked - wore blue camouflage uniforms of the kind used by police commandos. The women were not kidnapped, but had their mobile phones taken from them.

The Iraqi Islamic party, the largest Sunni Muslim group in the country, called the kidnapping "not only a crime but a major political farce".

"How can 50 new vehicles move in ... the area most heavily controlled by security agencies in the middle of the day?" the party said in a statement.

The Shia-dominated interior ministry has repeatedly denied any collusion with death squads operating in Iraq. The higher education minister is a member of the Iraqi Accordance Front, a Sunni group in the government.

In recent weeks, a university dean and a prominent Sunni geologist have been killed, bringing the death toll among education professionals to at least 155 since the war began in 2003.

This morning's car bomb ripped through a crowded market area in central Baghdad, according to police. The blast occurred in Rasheed Street, a popular commercial area in the Iraqi capital.

In Ramadi, police and medical workers said at least 31 Iraqis were killed in clashes. A medic at Ramadi hospital said those killed were civilians who died in shelling by US tanks. A police spokesman said 20 people were killed but gave no further information. Other reports suggested the death toll had risen to 30. The US military said it was investigating the reports.

In other violence, seven minivan passengers were killed and two wounded in an ambush near Mandali on the Iranian border, police said.

Mr Blair will give evidence privately this afternoon via videolink to the Iraq Study Group (ISG), whose forthcoming recommendations are expected to pave the way for changes in Washington's strategy on Iraq.

Downing Street gave no indication of what Mr Blair would say to the ISG except that he would ensure the US panel was "fully briefed on UK ideas".

However, his message was expected to be similar to that in a major speech to the City last night, when he raised the prospect of a new relationship with Iran and Syria.